CA2830345A1 - Method for producing a container for a bulk product - Google Patents

Abstract

The invention relates to a container (10) for a bulk product, comprising a housing (12) and a rubber-elastic force-generating body (24) protruding into the housing and having a filling space for receiving the bulk product. The force-generating body has a closed first longitudinal end and is suspended relative to the housing in the area of an opposite second longitudinal end. When being filled, the force-generating body expands radially and axially in the housing in such a manner that when a partially filled state is reached said body makes contact with a first wall part (16) of the housing (12) radially bounding the expansion, and when filling is continued the first longitudinal end approaches a second wall part (18) of the housing axially bounding the expansion as the axial enlargement of the area of contact between the force-generating body and the first wall part increases. Before the force-generating body is filled, at least one part the first wall part on the inside of the housing and/or at least one part of the outer face of the force-generating body is subjected to a friction-reducing surface treatment.

Description

Method for producing a container for a bulk product The invention relates to a method for manufacturing a container for a filling product, wherein the container comprises a housing and a rubber-like force-generating body projecting into the housing and having a longitudinal axis and a filling space for re-ceiving the filling product, wherein the force-generating body has a closed first longi-tudinal end and is suspended relative to the housing in the region of an opposite second longitudinal end, wherein the force-generating body, when being filled, ex-pands radially and axially in the housing - with respect to the longitudinal axis.
In a container of this kind, the elastic expansibility of the force-generating body can be utilized for generating a dispensing force which results from the tensile stress of the force-generating body and which is capable of forcing the filling product out of said body. The filling product may be, for example, a liquid, pasty, cream-like or gel-like substance which is intended to be dispensed in a metered manner by means of the container. For the purpose of metering the quantity dispensed, the container may be equipped with a valve system that can be actuated by the user.
In preferred configurations of the container, the dispensing force acting, in total, on the filling product results solely from the tensile stress of the force-generating body, i.e. it is possible to do without additional force-generating means in the form of a propellent gas or separate spring elements. Admittedly, it is understood that such additional force-generating means may be provided as a supporting measure if de-sired, although at least the predominant part of the dispensing force which is avalla-ble in total advantageously results from the tensile stress of the force-generating body.
As regards the prior art on the subject of receptacles having an elastically expansible force-generating body for receiving a filling product which is to be dispensed in a metered manner, the reader is referred to, for example, WO 2007/009651 A2, DE 103 10 079 Al, US 3,672,543, DE 43 33 627 C2, DE 201 20 143 Ul, DE 201 20 142 U1, DE 10 2004 005 881 Al and EP 0 361 091 Al.
In addition, the reader is referred to CH 591 901 A5 and also to EP 0 276 097 A2.
Both documents disclose an expansible filling bladder which is arranged in an outer housing of the cylindrical bottle type and which expands both radially and axially with respect to an axis of the housing on being filled. In the Swiss document, the bladder is intended to be accommodated in the final filling state without being substantially obstructed - either by the bottom of the housing or by the jacket of the cylinder.
According to the EP document, the filling bladder is intended, in the final filling state, to completely fill up the space available inside the housing and to press closely s against the wall of the housing.
In contrast to this, the starting point of the invention is a design of the housing and of the force-generating body such that, when being filled, said body expands radially and axially in the housing - with respect to the longitudinal axis - in such a way that, upon reaching a partial filling state, it abuts, particularly at a distance from the sec-ond longitudinal end, on a first wall portion of the housing that limits the expansion radially and, upon continued filling, the first longitudinal end approaches a second wall portion of the housing that limits the expansion axially with increasing axial enlargement of the area of abutment of the force-generating body on the first wall is portion.
If, in the case of such expansive behaviour of the force-generating body, the friction between said body and the housing is comparatively high, it may happen that the force-generating body unrolls, in the course of its expansion, substantially exclusively on the first wall portion of the housing, without any substantial slipping movement of the force-generating body on the said wall portion taking place. It has proved to be the case that this unrolling, or the absence of slipping, can lead to considerable axial forces which are exerted by the force-generating body upon the connecting means provided for suspending it within the housing, and thereby ultimately upon said housing. It has turned out that these axial forces may, under certain circumstances, be so great that detachment of the connection can occur en route between the force-generating body and the housing.
It is therefore an object of the invention to reveal a way in which, when the force-generating body is being filled, the risk of detachment of the latter through the oc-currence of excessive axial forces can be reduced.
For the purpose of achieving this object, the invention provides a method for manu-facturing a container for a filling product according to Claim 1. The container com-prises a housing and a rubber-like force-generating body projecting into the housing and having a longitudinal axis and a filling space for receiving the filling product, wherein the force-generating body has a closed first longitudinal end and is suspend-ed relative to the housing in the region of an opposite second longitudinal end.
When being filled, the force-generating body expands radially and axially in the hous-ing - with respect to the longitudinal axis - in such a manner that, upon reaching a partial filling state, it abuts, particularly at a distance from the second longitudinal end, on a first wall portion of the housing that limits the expansion radially and, upon continued filling, the first longitudinal end approaches a second wall portion of the housing that limits the expansion axially, with increasing axial enlargement of the area of abutment of the force-generating body on the first wall portion.
According to the invention, the method is distinguished by the fact that, prior to the filling of the to force-generating body, at least a part of the first wall portion is subjected to a fric-tion-reducing surface treatment on the inside of the housing and/or at least a part of the force-generating body is subjected to a friction-reducing surface treatment on the outside. The surface treatment may comprise the application of a friction-reducing substance to the first wall portion and/or the force-generating body.
Alter-natively or in addition, the surface treatment may comprise fluorination of the first wall portion and/or of the force-generating body.
If a friction-reducing substance is applied, it is preferable to provide at least the first wall portion of the housing with such a friction-reducing substance. However the possibility of also applying a friction-reducing substance, at least additionally, to the outer surface of the force-generating body should not be excluded. Since, however, the thickness of the layer of the substance applied becomes smaller as the expansion of the force-generating body increases (the same quantity of the substance has to be distributed over a surface that is constantly becoming larger), exclusive moistening of the force-generating body with the friction-reducing substance (without also applying such a substance to the housing at the same time) is regarded as not being pre-ferred, even though not excluded in principle.
The reduced friction between the force-generating body and the housing resulting from the surface treatment allows better slipping of the force-generating body on the first wall portion of the housing, and thereby facilitates the axial expansion of said force-generating body, minimizes axial force peaks of the latter on other components of the container and evens out the stresses in the material of said force-generating body. It has proved to be the case that, in this way, it is even possible to achieve shorter axial dimensioning of the force-generating body and to thereby reduce the input of material for each force-generating body manufactured, a fact which, in spite of the additional outlay for the surface treatment, can nevertheless lead to relevant cost savings overall in the context of mass production.
As the friction-reducing substance, use may be made, for example, of a water-based lubricant or even, in the simplest case, plain water. In addition to water, a water-based lubricant of this kind may contain, for example, glycerine as an additional constituent. In the case of forms of embodiment of this kind, the friction-reducing substance may, with time, evaporate partly or even substantially completely, alt-hough the friction, which is then increased again, between the force-generating body and the housing for the purpose of emptying said force-generating body will, as a rule, not have any disadvantageous effect, above all in view of the slowness with which emptying usually takes place, compared with the filling operation.
The application of the friction-reducing substance may be carried out, for example, by spraying, immersion, centrifuging or brushing on. Particularly if the friction part-ners (i.e. the housing and the force-generating body) both have low surface energy, it may be advantageous to achieve fine atomization by spraying the friction-reducing substance in order to thus be able to moisten the desired surface regions of the housing and/or of the force-generating body with the friction-reducing substance over a large area, because low surface energy aggravates the capacity for moisten-ing; one can say that liquids are inclined to run off a surface of low surface energy in droplets. If the surface energies of the friction partners permit, application of the friction-reducing substance may also be carried out by means of a roller or a brush, for example, or in an immersion process, instead of atomizing it.
The surface treatment may be restricted to those wall portions of the housing at which it is actually possible for expansion-induced, in particular axial, slipping of the force-generating body to occur. For example, it may be possible to leave the second wall portion of the housing, which restricts the axial expansion of the force-generating body and which may be arranged in a bottom region of the housing, free from the friction-reducing substance, if slipping movements that are, at most, negli-gible would occur at that point - even if there were lubrication.
As regards the choice of material, a silicone rubber, preferably an addition-cross-linking silicone rubber (particularly a liquid silicone rubber) is recommended for the force-generating body, although other elastomers (polyurethane, for instance) should not be excluded. A silicone-free and mineral oil-free lubricant should be used as the , friction-reducing substance, above all in the case of a silicone-based force-generating body.
Said friction-reducing substance may be a lubricant which can be wiped off and which does not adhere, even though the application of an adhesive lubricant, at least to the inside of the housing, is not excluded within the scope of the invention.
The carrying-out of a friction-reducing surface treatment is advisable, above all in the case of pairs of materials having comparatively high reciprocal friction.
Thus, for example, in the case of a housing produced from polyethylene or polypropylene, a comparatively high friction with the force-generating body can be identified, especial-ly if the latter is manufactured from a silicone rubber. Other plastics, too, may exhib-it comparatively high friction in relation to the surface of a silicone rubber body. To that extent, the invention is in no way restricted to housings made of PE
(polyeth-ylene) or PP (polypropylene). For example, it is possible, in principle, to conceive of using a housing made of PMMA (polymethyl methacrylate) or PTE (polyethylene terephthalate), in which case, however, the surface treatment should preferably produce a durable friction-reducing layer on the first wall portion and/or on the force-generating body. A durable friction-reducing layer of this kind may, for example, be formed by a non-evaporating lubricant which may then form a permanent barrier layer between the PMMA or PET material of the housing and the material of the force-generating body. The background is that numerous substances may tend to "dry-bond" with self-adhesive silicone (materials made of a liquid silicone rubber, for example, exhibit a self-adhesive property of this kind). This "dry-bonding"
comes about because of the formation of hydrogen bridges between the friction partners, which can lead to a durable connection. There is a fear of "dry-bonding" of this kind in the case of PMMA and PET, for which reason the surface treatment in the case of these plastic materials should form a durable barrier in relation to the material of the force-generating body. Polyethylene and polypropylene, on the other hand, have no oxygen atoms in their molecular make-up, a fact which avoids the formation of hy-drogen bridges to silicone. If a material without oxygen atoms in its molecular make-up is used for the housing, it is therefore not absolutely necessary to provide a dura-ble friction-reducing barrier between the housing and the force-generating body.
Instead, volatile lubrication may be sufficient at that point.
The shape of the housing may be, for example, bottle-like or can-like; that being the case, it may be, for example, approximately cylindrical or have regions of different diameter, for instance after the manner of a conical shape or with a more complex diametrical profile. In any case, the housing is longer than it is wide, under which circumstances the force-generating body is arranged in the housing with its longitu-dinal axis along the longitudinal extension of the latter. In the case of a housing s shape of this kind, which therefore obviously deviates from a spherical shape to-wards an elongated one, an expansion behaviour of the force-generating body in which the latter first abuts radially against a jacket part of the housing appreciably before reaching a specific, sought-after final filling state, and thereafter undergoes no substantial further radial expansion in this region, has turned out to be advanta-Even so, there is still sufficient space for further expansion of the force-generating body in the axial direction in this state. This permits, in particular, expan-sion behaviour in which the force-generating body, when being filled, initially begins to expand radially in an approximately central region of its axial length, and the radial expansion continues comparatively uniformly axially towards the closed end of the In a preferred form of embodiment, the first wall portion of the housing may have at The expansion behaviour of the force-generating body is preferably such that the an infeed volume which is at least 1.5 times, better at least 2 times, better still at least 2.5 times and preferably at least 2.8 times an infeed volume above which the force-generating body abuts radially on the first wall portion of the housing.
The expansion behaviour of the force-generating body may be such that the latter abuts radially on the first wall portion of the housing before reaching a degree of filling of 50%, better 45%, better still 40% and preferably 35% of an indicated nom-inal filling volume of the container. The nominal filling volume may, for example, correspond to a filling specification which is attached to the outside of the container and is directed at the purchaser or user. This may, for example, be printed on or With respect to an empty volume of the housing, i.e. the internal volume present in the empty housing (without the force-generating body), the expansion behaviour of the force-generating body may be such that the latter abuts radially on the first wall As regards the axial expansion, the expansion behaviour of the force-generating body may be such that, when being filled, the latter does not abut axially on the Alternatively or in addition, the expansion behaviour of the force-generating body It is preferable if, in the housing, the force-generating body is permitted a filling-In a preferred configuration, the force-generating body has an aperture in the region of its second longitudinal end and is connected, in this region, to a relatively rigid, annular connecting body which, in turn, is connected to at least one other container component, in particular at least one component of the housing, in the course of assembly of the container. In the process, the force-generating body may be manu-factured by injection technology and injection-moulded onto the connecting body.
According to another aspect, the invention provides a container for a filling product, wherein said container comprises a housing and a rubber-like force-generating body projecting into the housing and having a longitudinal axis and a filling space for re-ceiving the filling product, wherein the force-generating body has a closed first longi-tudinal end and is suspended relative to the housing in the region of an opposite second longitudinal end, wherein, when being filled, the force-generating body ex-pands radially and axially in the housing - with respect to the longitudinal axis - in such a manner that, upon reaching a partial filling state, it abuts, particularly at a distance from the second longitudinal end, on a first wall portion of the housing that limits the expansion radially and, upon continued filling, the first longitudinal end approaches a second wall portion of the housing that limits the expansion axially, with increasing axial enlargement of the area of abutment of the force-generating body on the first wall portion. In the course of the expansion of the force-generating body, the latter performs, at least in parts, a slipping movement on the first wall portion, wherein, for the purpose of influencing in a defined manner, and optionally preventing, the said slipping movement, the first wall portion has one or more, for example groove-like, recesses on its wall surface on the inner side of the housing in the area of abutment of the force-generating body. Said first wall portion may, for example, be designed with at least one groove-like recess which extends, in the peripheral direction of the housing, over the entire periphery, or only part of the periphery, of the latter.
The invention will be explained further below with the aid of the appended drawings, in which:
Fig. 1 represents an axial longitudinal section through a container constructed as a fire-extinguisher according to one embodiment;
Fig. 2 represents a spray head of the container in Fig. 1 in an enlarged view;

Figs. 3a to 3e represent axial sections through the container in Fig. 1 (leaving out a valve assembly) in various phases in the filling of a force-generating body;
Fig. 4 represents an exemplary diagram for graphically illustrating an operation for filling the container in Fig. 1; and Fig. 5 represents, diagrammatically, a phase in the process for manufacturing the container in Fig. 1, wherein a housing belonging to the container is sprayed on the inside with a lubricant in this phase.
The reader is referred, first of all, to Figs. 1 and 2. The container shown therein, which is designated by 10, is configured, by way of an example, as a manually port-able fire-extinguisher, although other forms of use, for instance as a dispenser for cosmetics, foodstuffs or technical substances, such as lubricants for example, are equally possible. In general, the container 10 serves for the storage and metered delivery of a filling product, under which circumstances the outer design of the con-tainer may be, for example, bottle-like or can-like (with a cylindrical or barrel-shaped basic shape, for example) or may assume any other desired shapes.
In the exemplary case shown, the container 10 has a housing 12 which is produced from polyethylene or polypropylene, for example, and has a housing axis 14, a gen-erally cylindrical jacket part 16 which encloses said axis 14 and a bottom part 18 which adjoins said jacket part 16 and closes the housing 12 axially on the underside.
In the region of the axially upper end, the jacket part 16 of the housing 12 extends radially inwards and forms a housing neck 20 with a housing aperture 22.
Suspended In the housing 12, more precisely in the region of the housing neck 20, is a rubber-like force-generating body 24 which projects into the interior space, which is designated by 26, of the housing 12. In the unfilled, non-tensioned state, said force-generating body 24 is of elongated design, after the manner of a condom, and has a longitudinal axis 28. In its interior, it forms a filling space 30 which serves to receive a filling product which can be sprayed and which, for example, foams.
In the exemplary case under consideration here, the filling product is an extinguishing agent, for instance in the form of an extinguishing gel or extinguishing liquid. The force-generating body 24 is manufactured, preferably from a silicone material, in particular liquid silicone rubber, in an injection-moulding process, with a closed end 32 which is rounded in a spherical manner and an aperture 34 which is formed at the opposite longitudinal end. Naturally, other rubber-like materials can equally well be used, for instance a polyurethane-based plastic. In the exemplary case shown, the force-generating body 24 is of single-ply construction, but it may optionally be coated comparatively thinly, on the inner and/or outer sides, with a durable layer made of s another material.
The force-generating body 24 is suspended in the housing 12 in such a way that, in the unfilled state, its longitudinal axis 28 extends substantially parallel to the housing axis 14, in particular approximately coincides with the latter. In the region of its open longitudinal end, it is connected to a connecting ring 36 which is produced from a comparatively rigid material of the lowest possible elasticity and is, in turn, con-nected to the housing 12. In the exemplary case shown, the connecting ring 36 has an axially extending section 38 by which it is inserted in the housing aperture 22.
This axially extending section 38 extends from an approximately annular-disc-shaped is section 40 which projects beyond said axially extending section 38 both radially in-wards and radially outwards. With its radially outer part, the annular-disc section 40 masks the housing neck 20, while it has, on its radially inner rim, an extension 42 which protrudes in the axially upward direction and serves for mounting a lid part 44 which consists, for example, of aluminium or tinplate. As a whole, the connecting ring 36 may be regarded as roughly T-shaped in cross-section, the axial section 38 forming the main leg of the T and the annular-disc section 40 forming the transverse leg of the T. In the exemplary case shown, the T-shape of the connecting ring 36 is modified slightly because of the presence of the extension 42 which protrudes in the axially upward direction.
For the purpose of fastening the connecting ring 36 to the housing 12, there may be provided, for example, an adhesive connection between the section 38, and/or the radially outer part of the section 40, and the housing 12. It is likewise possible to conceive of fixing the connecting ring 36 by means of a snap connection or clamping connection or by means of a thread or a bayonet fastener.
The connection between the connecting ring 36 and the force-generating body 24 is an integrally bonded one. More precisely, said force-generating body 24 is injection-moulded onto the connecting ring 36, for which purpose, in the course of the injec-tion-moulding operation, the connecting ring 36 may be placed, in the form of a prefabricated component, in the injection mould provided for the force-generating body 24. It will be recognised that the force-generating body 24 is injection-moulded onto the connecting ring 36 only on the radially inner side of the latter. The regions of the connecting ring 36 that are located on the outside, radially, are free from the material of the force-generating body 24. This is advantageous for the pressure conditions in the filled state; tensile stresses in the connecting region between the force-generating body 24 and the connecting ring 36 can be avoided better in this way.
For satisfactory adhesion of the connecting ring 36 to the force-generating body 24, said connecting ring 36 is preferably produced from a polyamide or from polybutyl-In its radially outer region, the lid part 44 is connected to the axial extension 42 of the connecting ring 36 by a crimp connection. A sealing ring 46, which is crescent-shaped in cross-section in the exemplary case shown, is inserted between the lid part The lid part 44 serves as a carrier for a valve assembly which is designated generally In the exemplary case shown, the force-generating body 24 is constructed, over a large part of its length which is located axially below (i.e. on the far side) of the con-35 axially as far as the point at which the wall of the force-generating body 24 starts to converge in the region of the closed end 32. This position is indicated diagrammati-cally at 58 in Fig. 1. At least in the axial hose region between the positions 56, 58, either (i) the wall thickness of the force-generating body 24 increases steadily to-wards the closed end 32 or (ii) the wall thickness remains the same but the diameter becomes steadily smaller towards said closed end 32 (on account of the wall thick-ness that remains the same, the decrease in diameter applies equally to the internal s diameter and to the external diameter). Both a linear growth in thickness and a linear decrease in diameter (with the wall thickness remaining the same) in the wall of the force-generating body 24 in the hose-shaped region favour expansion behav-iour such as is shown in Figs. 3a to 3e and as will be explained again afterwards. In the case of a growth in thickness, this may continue beyond the lower axial end of lo the hose region of the force-generating body 24, as far as the region of the closed end 32.
The force-generating body 24 may, for example, have, in the hose-shaped region, an inner peripheral face 60 that tapers conically towards the closed end 32 with respect 15 to the longitudinal axis 28, and also an outer peripheral face 62 that extends in a circular-cylindrical manner in relation to said axis 28. The angle (angle of widening-out of the wall thickness) formed between the conically tapering inner peripheral face and the cylindrical outer peripheral face is, for example, about 0.2 to 0.3 degrees.
Over an axial distance of, for example, about 10 cm, the growth in wall thickness 20 then corresponds to a few tenths of a millimetre (e.g. about 0.4 - 0.5 mm).
Alternatively, both the outer peripheral face and the inner peripheral face of the force-generating body 24 may extend in a conical manner, in which case they both taper towards the closed end 32 of said body. However, the tapering of the inner 25 peripheral face may be greater than that of the outer peripheral face resulting, over-all, in a growth in the wall thickness as it continues towards the closed end 32 of the force-generating body. The angle of widening-out of the wall thickness may, once again, have a value of the order of magnitude of tenths of a degree or may, under certain circumstances, be slightly smaller than before, since an effective reduction in 30 the diameter of the force-generating body is superimposed upon the growth in wall thickness on account of the tapering of the outer peripheral face.
As a further alternative, it is possible for only the diameter of the force-generating body 24 to be reduced in the hose-shaped region, with a constant wall thickness. In 35 this case, the inner peripheral face and the outer peripheral face are preferably both of conical design and both taper towards the closed end 32 with the same angle of tapering. The angle of reduction of the diameter may have a similar value (in the region of tenths of a degree) to that which the angle of widening-out of the wall thickness had previously.
Overall, the region of continuous increase in the wall thickness of the force-generating body 24 and/or of continuous reduction in the diameter extends over a major part of the axial overall length of the force-generating body 24, for example at least 70% or even at least 75%.
Axially above the start, which is supplied by the position 56, of the hose-shaped region, the force-generating body 24 may have a more complex wall geometry.
However, the axial length of this region is short, compared to the overall length of said force-generating body 24. In the exemplary case shown, the force-generating body 24 has, in the region of the axially lower end of the connecting ring 36, a point of enlarged wall thickness at which there is located a circumferential thickened por-tion 63 of the wall that protrudes radially inwards. Said thickened portion 63 of the wall helps to keep the stresses in the material of the force-generating body 24 low in the region of the axially lower end of the connecting ring 36. At the same time, said thickened portion may serve as a de-moulding aid for the mould core of the injection mould used for manufacturing the force-generating body 24.
The reader is now referred to Figs. 3a to 3e. Fig. 3a shows the unfilled state of the force-generating body 24. It can be seen that said force-generating body 24 is at an axial distance from the bottom part 18 of the housing 12. It is also at a radial dis-tance, all the way round, from the jacket part 16, this applying at least to that region in which the force-generating body 24 is capable of stretching radially and is very largely unhindered by the connecting ring 36 from expanding radially.
When the force-generating body 24 is filled with extinguishing agent (or filling prod-uct in general), said body starts to expand. Figs. 3b, 3c, 3d and 3e show states of expansion of the force-generating body 24 at different degrees of filling, until a final filling state is reached (Fig. 3e). In the final filling state, the volume fed in depends upon a nominal filling quantity predetermined for the container 10 and is, in any case, greater than said quantity.
The dead volume of the force-generating body 24 (internal volume in the unfilled state) may be kept small by the provision of a volume-displacer (of which no further details are represented).

The expansion of the force-generating body 24 takes place in both the radial direc-tion and the axial direction. It will be seen that the radial expansion is initially great-est approximately in an axial central region of the force-generating body 24 (centrally with respect to its particular axial length). At a sufficient degree of filling, the force-generating body 24 finally abuts on the jacket part 16 all the way round (Fig.
3c). As a result of this, there are separated off, axially above and below the area of abut-ment in which the force-generating body 24 bears against the jacket part 16, two partial spaces 64, 66 between the housing 12 and the force-generating body 24, the volumes of which spaces increasingly diminish as the filling of the force-generating body 24 continues. In the process, the area of abutment in which the force-generating body 24 bears against the jacket part 16 continues to expand in both axial directions, i.e. axially downwards and also axially upwards (although to a great-er extent axially downwards). The jacket part 16 forms a first wall portion, within the meaning of the invention, that limits the radial expansion.
In the final filling state, the force-generating body 24 has expanded axially to at least close to the bottom part 18 of the housing 12 and lies flat at that point, preferably in an approximately spherical bottom trough 68 (see Fig. 3d). In this state, the force-generating body 24 bears against the jacket part 16 over a large part of the axial length of said jacket part. The impinging of the force-generating body 24 against the bottom part 18 preferably takes place shortly before the nominal filling quantity is reached, for example only after the feeding-in of at least 80%, better at least 85%
and better still at least 90% of the nominal filling volume of the container 10. With such expansion behaviour of the force-generating body 24, it is possible to avoid introversion of said body in the region of the bottom part 18, at least as long as the filling product which has been fed in does not freeze and thereby increase its vol-ume. The bottom part 18 forms a second wall portion, within the meaning of the invention, that limits the axial expansion.
The tensile stress stored within the force-generating body 24 brings about a force which acts upon the filling product that has been fed in, and by which force said filling product is forced out the container 10 when the valve assembly 48 is actuated.
No other force-generating means are present in the container 10 shown. The dis-pensing force is applied completely by the force-generating body 24.

The filling quantity (filling volume) which is to be fed in until the final filling state is reached may be, for example, between 105% and 115% of the nominal filling quan-tity assigned to the container 10. It is preferable if, in the course of the filling of the container 10, so much filling product is fed in that the total quantity fed in corre-sponds to the nominal filling quantity, plus the initial volume of air in the filling space 30 when the force-generating body 24 is in the unfilled state, plus an additional volume. This additional volume serves to compensate for losses which may result from a decreasing restorability of the - stretched - force-generating body 24 and from an escape of fractions of the filling product through the wall of said body. For example, the additional volume may be at least as great again as the initial volume of air in the filling space 30 of the un-stretched force-generating body 24.
Figure 4 shows, by way of examples, qualitative progressions for the axial elongation (characteristic curve 1) and the widening-out of the diameter (characteristic curve 2) during the filling of the container 10. Up to a filling volume VI, the force-generating body 24 is able to expand both axially and radially without being restricted by the housing 12. Upon reaching the filling volume VI, the force-generating body 24 comes into contact with the jacket part 16 of the housing 12 for the first time. This corresponds to the state shown in Figure 3c. The term "force element" used in Fig-ure 4 refers to the force-generating body 24; "wall" means that part of the housing wall which is formed by the jacket part 16.
After the filling volume V1 is exceeded, the area of abutment in which the force-generating body 24 bears against the jacket part 16 expands in the axial direction, but no further widening-out of the diameter of said force-generating body 24 takes place. That is why, in the diagram in Figure 4, the characteristic curve 2 changes into a horizontal straight line from the filling volume VI onwards. At the same time, the tip of the force-generating body 24 (i.e. its closed end 32) is displaced axially further towards the bottom part 18. In the diagram in Figure 4, this is indicated by a continued rise in the characteristic curve 1 beyond the filling volume V1.
On reaching a filling volume V2, the axially lower end 32 of the force-generating body 24 impinges upon the bottom part 18 of the housing 12. That is when the filling operation is terminated, if not before. Beyond this point at which the force-generating body 24 impinges upon the bottom part 18, no further filling, or at least no significant further filling, takes place. The feeding-in operation may optionally be terminated even before the force-generating body 24 impinges upon the bottom part 18. In any case, the filling volume V2 at which the filling operation is terminated lies above the nominal filling volume of the container 10. In order to give an example in numerical terms, the total filling volume V2 fed in might be about 900 cm3 for an indicated nominal filling volume of the container of 800 cm3.
The diagram in Figure 4 makes it clear that the first radial abutment of the force-generating body 24 on the jacket part 12 takes place comparatively early, before the final filling state (filling volume V2) is reached. The filling volume V1 may, for exam-ple, be between 20% and 50%, and preferably between 25% and 40%, of the filling volume V2. In other words, the filling volume V2 is at least 2.0 times, for example about 3.0 times, the filling volume V11 or even a still larger multiple thereof. With respect to the nominal filling volume specified for the container 10, the filling volume V1 may be, for example, about 30% to 35% of said nominal filling volume. As an alternative to the nominal filling volume, it is also conceivably possible to use the empty volume of the housing 12 as a reference. This is understood to mean the volume of the inner space 26 of the housing with the force-generating body 24 miss-ing. With respect to such an empty volume of the housing 12, the filling volume Vi may, for example, be between, say, 20% and 30%.
zo Overall, the widening-out of the diameter of the force-generating body 24 until it impinges upon the jacket part 16 may be, for example, between 200% and 300%, and the axial elongation on reaching the filling volume V2 may be, for example, be-tween 80% and 150%.
The free space which is present, in the unfilled state, axially underneath the force-generating body 24 as far as the bottom part 18 of the housing 12 is so dimensioned that said force-generating body 24 abuts axially on the bottom part 18 only after the feeding-in of a filling quantity that exceeds the nominal filling volume of the contain-er 10, that is to say after more than 100% of the nominal filling volume. For exam-pie, it may be that abutment of the force-generating body 24 on the bottom part 18 takes place only after the feeding-in of at least 110% or even at least 120%
of the nominal filling volume of the container 10. Referred to the empty volume of the housing 12, on the other hand, the axial free space underneath the force-generating body 24 may be so dimensioned that abutment of said body on the bottom part 18 does not take place before at least 85% and preferably at least 90% of the empty volume of the housing are fed into the force-generating body 24.

The friction between the inner surface of the housing 12, in particular the inner sur-face of the jacket part 16, and the outer surface of the force-generating body 24 may be considerable. This particularly applies to the case where the force-generating body 24 is manufactured from a silicone rubber. Silicone materials often have a surface which permits anything but smooth sliding. If, in addition, the housing 12 is produced from a plastic, in particular polyethylene or polypropylene, the result may easily be a pairing of materials between the housing 12 and the force-generating body 24 that prevents almost any slipping (sliding).
However, it has proved to be the case that, in the expansion phase of the force-generating body 24, when the latter is already bearing radially against the jacket part 16 of the housing 12, slipping of said force-generating body 24 along said jacket part 16 in the axial direction is advantageous, in order to avoid excessively high axial forces on the connecting ring 36, which forces, under certain circumstances, can even lead to detachment of said connecting ring 36 from the housing 12. In the sequence of pictures in Figures 3a to 3e, the force-generating body 24 should there-fore, in the situations in Figures 3c and 3d, be able to slip axially along the jacket part 16 of the housing 12 in order to avoid such force peaks and ensure a properly proportioned distribution of the stresses in the material of the force-generating body 24. For this purpose, during the manufacture of the container 10, and more precise-ly prior to the installation of the force-generating body 24 in the housing 12, the inner surface of said housing 12 is sprayed, at least in the region of the jacket part 16, with a friction-reducing substance, such as is represented diagrammatically in Figure 5. Said friction-reducing substance is preferably a water-based lubricant (e.g.
with glycerine as an additional main constituent) which may at least partly evaporate with time. On the other hand, a silicone-based or mineral oil-based lubricant should not be used if use is made of a force-generating body made of silicone rubber, since the lubricant could attack the material of said body.
According to Fig. 5, the lubricant is sprayed, for example, by means of a spraying bar 70 which may be introduced into the housing 12 through the neck 20 of said hous-ing. By means of the spraying bar 70, the jacket part 16 may be sprayed over at least part of its axial length and, if desired, the bottom part 18 of the housing 12 may also be sprayed on the inside with the lubricant. A spraying control unit 72, which is indicated diagrammatically, controls the spraying operation.

After the lubrication of the housing 12 on the inside and the removal of the spraying bar 70 from said housing 12, the force-generating body 24, which has been pro-duced separately beforehand, is then inserted (together with the connecting ring 36 adhering to it), in the housing 12 during the assembly of the container 10, and is connected to said housing. This is indicated diagrammatically in Fig. 5 by an arrow 74. The container, having been finally assembled, can then be filled with the desired filling product, after the valve assembly 48 (or other suitable valve means) have also been attached beforehand.
io Alternatively or in addition to the application of a lubricant, a reduction in friction between the housing 12 and the force-generating body 24 can be obtained by fluori-nation of at least one of the two surfaces forming the friction pairing. The surface properties can be altered, and the friction thereby also reduced, by fluorination. As a rule, both silicone materials and other plastics can be satisfactorily fluorinated. The fluorine compounds created by fluorination on the surface of the body treated in this way are, as a rule, comparatively stable, so that fluorination is eligible for considera-tion not only when, but especially when, there is a risk to the materials of the hous-ing 12 and of the force-generating body 24 of "dry-bonding" as a result of the formation of hydrogen bridges. As a result of fluorination, it is then possible to pro-vide a durable separating layer which prevents the formation of such hydrogen bridges or at least reduces their number.
In Figs. 1 and 3a to 3e, there can clearly be seen a number of radial recesses constructed in the jacket part 16 of the housing 12, in which connection the term "recess" should be understood here from the viewpoint of an observer looking at the jacket part 16 from the inside of the housing. In the exemplary case shown, said recesses 76 are groove-like and extend in the peripheral direction of the jacket part 16. They may, for example, pass over the entire periphery of the housing.
Alterna-tively, a number of recesses 76 may be arranged at intervals, one behind another in the peripheral direction, in an axial plane. In addition, in the exemplary case shown, recesses 76 of this kind are provided one above another in a number of axial planes.
At least some of the recesses 76 are located in a region of the jacket part 16 in which the force-generating body 24 abuts, in the course of its expansion over the recess 76 in question, on the jacket part 16, under which circumstances the force-generating body 24 is able to expand to a slightly greater extent in the region of the recess 76, i.e. is able to expand into the latter. This brings about a "latching", so to speak, of the force-generating body 24 in the recess 76 in question, so that a slip-ping movement of the force-generating body In relation to the jacket part 16 may be restricted or even prevented locally at that point. In the light of Figs. 3d and 3e, such "latching" of the force-generating body in relation to the housing 12 may, for example, take place in the recesses which are identified by 76' therein, because it is these recesses 76' which the force-generating body 24 completely masks until the final filling state is reached.

Claims (13)

1. A method for manufacturing a container (10) for a filling product, wherein the container comprises a housing (12) and a rubber-like force generating body (24) projecting into the housing and having a longitudinal axis (28) and a filling space (30) for receiving the filling product, wherein the force-generating body has a closed first longitudinal end (32) and is suspended relative to the housing in the region of an opposite second longitudinal end, wherein the force-generating body, when being filled, expands radially and axially with respect to the longitudinal axis in the housing in such a manner that it abuts on a first wall portion (16) of the housing (12), preferably at a distance from the second longitudinal end, upon reaching a partial filling state, the first wall portion limiting the expansion radially, and that upon continued filling the first longitudinal end (32) approaches a second wall portion (18) of the housing (12) while the area of abut-ment of the force-generating body on the first wall portion progressively axially in-creases, the second wall portion delimiting the expansion axially, wherein in the manufacturing method, prior to filling the force-generating body, at least a part of the first wall portion (16) is subjected on a housing inner-side to a friction-reducing surface treatment and/or at least a part of the force-generating body (24) is subjected on an outside thereof to a friction-reducing surface treatment.

2. The method of claim 1, wherein the surface treatment includes applying a friction-reducing substance to at least one of the first wall portion (16) and the force-generating body (24).

3. The method of claim 2, wherein the friction-reducing substance is applied through a spraying, immersion, centrifuging or brush process.

4. The method of claim 2 or 3, wherein a water-based lubricant is used as the friction-reducing substance.

5. The method of any one of claims 2 to 4, wherein a lubricant that is free of silicone-based or mineral oil-based components is used as the friction-reducing sub-stance.

6. The method of any one of claims 2 to 5, wherein a non-adhesive lubricant is used as the frication-reducing substance.

7. The method of any one preceding claim, wherein the surface treatment in-cludes a fluorination of at least one of the first wall portion (16) and the force-generating body (24).

8. The method of any one preceding claim, wherein the housing (12) is made of polyethylene or polypropylene.

9. The method of any one of claims 1 to 7, wherein the housing is made of polymethyl methacrylate or polyethylene terephthalate and the surface treatment brings about a permanent friction-reducing coating on at least one of the first wall portion (16) and the force-generating body (24).

10. The method of any one preceding claim, wherein the force-generating body (24) is made of a silicone rubber.

11. The method of any one preceding claim, wherein the first wall portion (16) has at least one recess, for example a groove-like recess, at a housing inner-side wall surface in the area of abutment of the force-generating body.

12. A container manufactured in accordance with any one preceding claim.

13. A container (10) for a filling product, wherein the container comprises a hous-ing (12) and a rubber-like force-generating body (24) projecting into the housing and having a longitudinal axis (28) and a filling space (30) for receiving the filling prod-uct, wherein the force-generating body has a closed first longitudinal end (32) and is suspended relative to the housing in the region of an opposite second longitudinal end, wherein the force-generating body, when being filled, expands radially and axially with respect to the longitudinal axis in the housing in such a manner that it abuts on a first wall portion (16) of the housing (12), preferably at a distance from the second longitudinal end, upon reaching a partial filling state, the first wall portion limiting the expansion radially, and that upon continued filling the first longitudinal end (32) approaches a second wall portion (18) of the housing (12) while the area of abut-ment of the force-generating body on the first wall portion progressively axially in-creases, the second wall portion delimiting the expansion axially, wherein during the expansion of the force-generating body (24) at least portions of the force-generating body perform a sliding movement on the first wall portion (16), wherein the first wall portion (16) has one or more recesses, for example groove-like recesses, at a housing inner-side wall surface in the area of abutment of the force-generating body.